Production of liquid carbon dioxide



July 27, 1943. w. DENNls PRODUCTION OF LIQUID CARBON DIOXIIDE Filed Oct.29, 1941 kw Iv beverages.

Patented `uly 27, 1943 UNITED lSTATES PATENT .OFFICE l 2,525,045PRODUCTION or LIQUID CARBON Dioxins Wolcott Dennis, Stamford, Conn.,assignor to AirA Reduction Company, Incorporated, New York, N. Y., acorporation of New York Application October 29, 1941, Serial No. 417,003

12 Claims. (Cl. 62'- 91.5)

This invention relates 4to the production of liquid carbon dioxide andparticularly to the conversion of solid carbon dioxide to the liquidphase.

Liquid carbon dioxide Yhas been produced and marketed in cylinders underpressure for many years and has been utilized for many industrialpurposes including, for example, carbonation of In recent years, owingto the large industrial production of solid carbon dioxide, much of thismaterial has been utilized by conversion to the liquid phase. A simplemethod of conversion consists in permitting the solid carbon dioxide toliquefy in a suitable container from which the liquid is withdrawn anddelivered, at the high pressure developed within the container, to thecylinder in which it is transported. In another method, the solid carbondioxide is liquefied and thenpermitted to vaporrearlier methods resultsfrom the fact that oil is used as a plasticizer in the manufacture ofsolid carbon dioxide. 'The oil which is retained in the solid carbondioxide enters the liqueer and inevitably contaminates the liquidproduct. When such liquid is utilized for'industrial purposes, andespecially in the carbonation of beverages, the oil, even in the smallproportions present, imparts an unsatisfactory taste and odor to thebeverage or other material treated, and not infrequently spoils thematerial so that it cannot be disposed of in commerce.

It is the object of the present invention to avoid the diii'icultiesmentioned and especially to simply and easily eliminate substantiallyall of the oil which may be present from the liquid product.

Another object of the invention is the provision of a method andapparatus permitting large scale conversion of solid carbon dioxide intoliquid dioxide which is substantially free from oil impurities.

Another object of the invention is the provision of a method andapparatus for converting duced thereto. Furthermore, the maintenance ofsures a better product than has been ,available as the result of methodsheretofore in use.

Other objects and advantages of the invention will be apparentI as it isbetterunderstood by references to the following speciiication andaccompanying' drawing, which diagrammatically illustrates an apparatussuitable for the practice of the invention.

I have discovered that it is possible to filter substantially all of theoil which may be carried over from the liqueiier by the gaseous carbondioxide released as vapor therein, provided the filtrationisaccomplished at pressures below 300 pounds per square inch gauge andpreferably in the neighborhood of 150 pounds per square inch gauge.Moreover, if the liqueers are operated at relatively low pressures,above the triple point pressure, for example from 60 to 150 pounds persquare inch gauge, most of the oil introduced with the solid carbondioxide remains in the liqueer because of the relatively low temperaturethereof and can be removed therefrom'before a fresh charge of solidcarbon dioxide is introlow pressures in the liqueers permits the use ofreceptacles capable of holding a ton or more of solid carbon dioxide atthe charge without unduly increasing the weight of the liqueer in Orderto aio'd the strength required to permit maintenance of high pressures.

In carrying out the invention, I prefer to employ two liqueiiers whichafter the operation is started are charged alternately with solid carbondioxide. The melting and vaporization of the solid carbon dioxide is-facilitated by an application of a heating agent such as steam,controlled to permit operation in the desired manner. The liqueers maybe constructed of suitable material such as steel and designed towithstand pressures of.200 pounds per square inch gauge with the usualsafety factor. The pressure indicated is merely indicative of thepreferred pressure limit for the liqueler, as higher pressures can I ofcourse be used.

solid carbon dioxide into liquid carbon dioxide When a portion of thesolid carbon dioxide in one of the liquefiers has been liquefied to thedesired extent, carbon dioxide vapor is withdrawn continuously, passedthrough a temperature exchanger and delivered to a compressor where thepressure is increased to the desired p'oint. which, for example, may beapproximately 150 pounds per square inch gauge. Thus the vapor may bewithdrawn at a pressure of pounds per square inch gauge or higher andcompressed to the desired pressure. The temperature is raised bycompression, and consequently the vapor is passed through a cooler inwhich it is subjected to heat exchange with water orother suitablecooling agent. It passes thence to a filter which may be illed withcotton or other suitable material which is adapted to remove the oilfrom the vapor. As previously indicated, such a filter is effectiveprovided the pressure of the vapor is below 300 pounds per square inchgauge, and it is particularly effective at pressures in the neighborhoodof 150 pounds per square inchgauge, at which point it is possible toremove substantially all of the oil present in the vapor, or, in anyevent, to reduce the proportion of oil to the point where it is nolonger detectable in the liquid product or in products treatedtherewith.

From the filter, the vapor returns through the exchanger previouslymentioned, where it is cooled by heat exchange with the vapor leavingthe liqueer. I t is then delivered to a coil in the liqueer from whichthe vapor was withdrawn, until such time as the amount of solid orliquid carbon dioxide remaining in that lique'- fier is sufficient toeffect the condensation of the vapor. Thereafter the vapor may bedirected through a corresponding coil in the companion liqueer. The-liquid resulting from the condensation is delivered to a receiver, fromwhich it is withdrawn by a liquid carbon dioxide pump which delivers theliquid at the required pressure to the filling manifold and thence intothe cylinders.

As will be observed from the foregoing description, carbon dioxide inthe vapor phase is withdrawn at relatively low pressures from theliquefier in which the pressure is never permitted to develop above thepoint at which the vapor isremoved. The vapor, after giving up its lowtemperature, is recompressed to a pressure which is still relatively lowand at which the oil content may be removed readily by simplefiltration. Thereafter, the vapor, after being initially cooled l byheat exchange with vapor leaving the liqueer, is subjected to heatexchange with liquefy` ing solid carbon dioxide to convert it to theliquid phase. The liquid is still at low pressure and is then pumped tothe desired pressure which it is necessary to maintain in the filledcylinders.

In order that the invention may be more clearly understood, reference ismade to the accompanying drawing. sures and other details hereinaftermentioned are merely illustrative of the preferred embodiment of theinvention in its practical application to'commercial production ofliquid carbon dioxide. Other pressures and temperatures may be used, solong -as the fundamental purpose is maintained, that is, the withdrawalof carbon dioxide vapor from the liqueer at relatively low pressure,filtration of the vapor at low pressure, and condensation of the vaporto liquid while the vapor is still at low pressure by heat exchange withmelting solid carbon dioxide. tion as thus carried out is economicalboth with respect to the installation and maintenance of the apparatusand the power consumed in the operation. It ensures the production ofliquid carbon dioxide which is free from oil contamination.

Referring te the drawing, 5 and 6 indicate liqueflers of suitableconstruction, the details of which form no part of the presentinvention. The liqueers are provided with steam compartments 1, 8, 9 andI0, which are adapted to be 'I'he temperatures and pres-- Theoperasupplied with steam from a suitable source through pipes II, I2, I3and I4, suitable valvesA in order to regulate the operation ashereinafter described. The liqueers 5 and 6 are also provided with coilsI6 and I1, the purpose of which will be explained hereinafter. A pipe I8is connected by branches to both of the liqueers 5 and 6 and to a heatexchanger I9 of usual construction. From the exchanger the vapordelivered through the pipe I8 passes through a pipe 26 to a compressor2I where its pressure is increased to the desired point. A pipe 22delivers the compressed vapor to a trap 23 which separates any liquidtherein contained, and the vapor is delivered through a pipe 24 to acooler 25 supplied with water or other suitable cooling agent to a. pipe26. The Water escapes through a pipe 21 and may be delivered to the head26 of the compressor to eiect the cooling thereof and thence wastedthrough a pipe 29.

The vapor is delivered through a pipe 30 from the cooler 25 to a filter3I which as hereinbefore indcated may be filled with cotton or othersuitable filtering material which removes oil from the vapor. Thence thevapor passes through a pipe 32 to the exchanger I9 and is deliveredthrough a pipe 33 and branch 34 to the coil I6 in the liqueer 5 oralternately through a branch 35 to the coil I1 and the liquefler 6. Fromeither of the coils the condenser vapor or carbon dioxide liquid iswithdrawn through branches 36 and 31 to a pipe 33 which delivers theliquid to the liquid receiver 39. Thence it is withdrawn through a pipe49 and compressed by the liquid carbon dioxide pump 4I. 'Ihe compressedliquid is delivered through a pipe 42 to the filling manifold, (notshown). A pipe 43 connected to the liquid carbon dioxide pump returnsany vapor which is formed by evaporation of the liquid through branches44 and 45 to the liqueers 5 and 6, so that the vapor is returned to thecycle.

In the operation of the apparatus'bOth of the liqueiiers 5 and 6 areinitially charged with solid carbon dioxide, and steam is supplied inquantity sufficient to cause the solid carbon dioxide to partially melt.When the liquid level in the liqueer 5 has reached the point Where theliqueer is approximately. half filled with liquid, the vapor iswithdrawn through the pipe I8. At this point no vapor is withdrawn fromthe liquefler 6,' and heating is discontinuad in the latter liqueer whenthe liquid level is such that the liqueer is approximately one-quarterfilled with liquid. The temperature in both liqueers will be atapproximately -70 F. The vapor withdrawn from the liquefler 5 atpressures preferably between 60 and 150 pounds per square inch gaugepasses through the exchanger I9 and thence to the compressor 2|, wherethe pressure is increased, if necessary, to approximately pounds persquare inch gauge. In passing through the exchanger I9, the vapor whichis approximately at 70 F. has its temperature raised to approximately 68F. After compression, the vapor is at approximately 167 F. and is cooledin the cooler 25 to approximately 86 F. At the latter temperature and ata pressure'of approximately 150 pounds per square inch gauge. the vaporpasses through the filter 3| which removes the oil. Thereafter the vaporin passing through the exchanger'IS is reduced in temperature toapproximately 33 F. and is delivered to the coil I6 in the liquefler 5.The vapor is readily condensed and is delivered to the receiver 39 at atemperature of approximately '-43 F.' When .the liquid level in theliqueer has been reduced by vaporization, owing to the introduction ofsteam and the passage of vapor through the coil I6, to the point wherethe lique- A fier is only about one-quarter filled with liquid,

` the liquid level reaches the point where the liquefier isapproximately one-quarter lled with liquid. At this point the steam isshut off and the liquef'ler is held in reserve until such time as it maybe necessary in accordance with the cycle to divert the filtered carbondioxide vapor through the coil I6. Meanwhile the vapor passes throughthe coil I'I in the liquefier 6, is liquefied and delivered .to theliquid carbon dioxide receiver 3'9 as previously described. The cycle iscontinued by alternately filling the liqueflers 5 and 6 with solidcarbon dioxide and controlling the conversion of the solid to liquid andvapor phases inthe manner hereinbefore described.

As will be readily understood, many of the details such as pressuregauges, sight gauges, pressure relief valves, drain pipes'and othervalves i which are common to this type of apparatus are not illustratedand described, since they form nov part of the invention and would beapplied and utilized in similar arrangements by anyone skilled in theart. The omission of such illustration and description is merelytosimplify the specification and to clarify the invention and theessential features thereof.

The method and apparatus as described has been demonstrated in practicaloperation to afvford considerable economy, both in installation andmaintenance, but it is particularly effective in the large scaleproduction of liquid carbon dioxide free from oil contamination.

vVarious changes may be made in the form and arrangement of theapparatus as well as in/ the details of operation without departing fromthe invention or sacrificing the advantages thereof.

I claim: 1. The method of converting solid carbon dioxide to the liquidphase which-comprises subjecting vapor from the solid carbon dioxide ata pressure below 300 pounds per square inch gauge to filtration toremove oil therefrom and thereafter conducting the vapor in heatexchange, relation with solid carbon dioxide, thereby condensing-thevapor, and withdrawing the liquid product.

2. The lmethod of converting solid carbon dioxide to the liquid phasewhich comprises suband thereafter conducting the vapor in heat exchangerelation with solid carbon dioxide,` thereby condensing the vapor, andwithdrawing the liquid product.

4. The method of converting solid carbon dioxide to the liquid phasewhich comprises heating the solid carbon dioxide, withdrawing andcompressing vapor therefrom and conducting the vapor in heat exchangerelation with solid car- `bon dioxide, thereby condensingthe vapor.

' 5. The method of converting solid carbon di-l oxide 'to the liquidphase which comprises Vheating the solid carbon dioxide, withdrawing andcompressing` vapor therefrom, filtering the vapor` to 1 remove oiltherefrom and conducting the vapor in heat exchange relation with solidcaring the solid carbon dioxide, withdrawing andA compressing vaportherefrom to a pressure between 60 and 150 pounds per square inch gauge,filtering the vapor at that pressure to remove oil therefrom andconducting the vapor in heat exchange relation with solid carbondioxide, thereby condensing the vapor.

. 8. The method of converting solid carbon dioxide to the liquid phasewhich comprises heating separate masses of solid carbon dioxide,withdrawing vapor from one of the masses, compressing the vapor andreturning it in heat exchange relation with the mass from which itwaswithdrawn until the latter is substantially exhausted and then insimilar relation with the other mass, thereby condensing the vapor.

drawing vapor from one of the masses, compressing the vapor, ltering thevapor to remove oil therefrom and returning it in heat exchange relationwith the mass from which it was withdrawn'until the latter issubstantially exhausted and then in similar relation with the other massthereby condensing the vapor.

10. The method of rconverting solid carbon dioxide to the liquid phasewhich comprises heating separate4 masses of solid carbon dioxide,withdrawing vapor from one of the masses, compressing the vapor to apressure below 300 pounds per square inch gauge, filtering the'vapor atthat pressure to remove oil therefrom and returning it in heat exchangerelation with the mass. from which it was withdrawn until the latter issub'- stantially exhausted and then in similar relation with the othermass thereby condensing the- Vapor.

pounds per square inch gauge, filtering the vapor at that pressure toremove oil therefrom' and returning it in heat exchange relation withthe mass from which it was withdrawn until the latter is substantiallyexhausted and then in similar relation with the other mass, therebycondensing the vapor.

12. The method of converting solid carbon dioxide to the liquid phasewhich comprises heating separate masses of solid carbon dioxide,withdrawing vapor from one of the masses, compressing the vapor,returning it in heat exchange relation with the mass from which it waswithdrawn until the latter is substantially exhausted and then insimilar relation with the other mass thereby condensing the vapor. andthereafter withdrawing vapor from said other mass and repeating thecycle.

WOLCOTT DENNIS.

